Epoxy resins are cured with a variety of curing agents into cured products generally superior in mechanical properties, water resistance, chemical resistance, heat resistance, electrical properties, and the like, and have been used, for example, as adhesives, paints, laminated plates, molding materials, and casting materials in a wide range of industrial fields. Conventionally, the epoxy resins that have been used most widely are bisphenol A epoxy resins. Acid anhydrides and amine compounds are known as the curing agents for epoxy resins, but phenolic novolak resins are often used in the field of electric and electronic parts for the purpose of improving reliability, for example, of heat resistance. Flame retardants are often used for the purpose of improving flame resistance of the cured products, and bromine-containing compounds such as tetrabromobisphenol A and the epoxidized derivatives thereof, and the reaction products from tetrabromobisphenol A and a bisphenol A epoxy resin are generally known as such flame retardants.
However, although the bromine-containing compounds described above are effective in making resins superior in flame resistance, they are pointed out to generate the substances possibly causing environmental pollution during disposal and incineration. In addition, there is also a concern about the toxicity of the antimony compounds that are used as the flame retardant aids. Among the recent enhanced recognition about environmental protection, there is an increasing need for halogen-free and antimony-free epoxy resin compositions. In addition, cured epoxy resins prepared by using a phenolic novolak as the curing agent are superior in reliability, but the cured products are rigid and lack flexibility. There are recently various electric and electronic parts different in shape, and in addition to plate-shaped parts using conventional large package and rigid base plates containing glass textile as a base material, sheet-shaped parts (shaped products) using a flexible sheet-shaped base material such as polyimide film, PET (polyethylene terephthalate) film, or metal foil have been developed. The shaped products are usually produced by coating an epoxy resin composition in the form of varnish on a sheet-shaped base plate, removing the solvent, and then curing the coated epoxy resin composition. In such a case, the cured product obtained should be sufficient flexible and highly adhesive to the base material, for example, of polyimide. The cured product should also have a high heat resistance, from the viewpoint of the reliability of the resulting electric and electronic parts.
Separately, an epoxy resin composition containing an epoxy resin, a phenol resin and a phenolic hydroxyl group-containing aromatic polyamide resin was disclosed as an epoxy resin improved in the fragility associated with conventional epoxy resin compositions in JP-A No. 2000-313787, and was described to have a high heat resistance and toughness. However, the flexibility and the flame resistance thereof, which are able to be used for a sheet-shaped base plate, are not described there and seem to be still unsatisfactory.